Various e-mail server applications may include an auto-discovery feature that simplifies an enrollment of a client device with the e-mail server. The auto-discovery feature can return system settings to the client device after a user enters only his or her e-mail address and password. Previously, the user may have had to enter other information, such as internet protocol (IP) addresses, post office protocol (POP) settings, server settings, and other settings that may be unknown to the user. However, for an e-mail server application to include the auto-discovery feature, an e-mail server must be installed on-premises with a dedicated IP address and a digital certificate. The digital certificate must be unique and correspond to a single domain.
Some auto-discovery applications employ the secure sockets layer (SSL) protocol to provide a secure connection between a client application (e.g., a web browser) and network content (e.g., websites). SSL certificates are issued by a certificate authority after an identity of an entity applying for the certificate has been verified. When a client application requests a secure connection to a particular domain, the client application retrieves a digital certificate for the domain, determines whether the digital certificate has expired, and determines whether the domain matches a domain specified in the digital certificate. If the digital certificate is invalid or has expired, a secure connection will not be established.